How Many Hours of Sun Does a Lavender Plant Need?

Lavender **(Lavandula spp.) grows best when it gets sun all day. An aromatic herb, lavender grows in open fields as a cultivated crop in its native Mediterranean climate. This rugged plant not only withstands exposed environments but actually needs an open location that receives sunlight all day. In the home garden, plant lavender as a specimen plant or with other sun-loving perennials in a site exposed to full sun with good air circulation and well-draining soil**.

In the humid U.S. Deep South or any location with poorly draining soil, grow lavender in containers with bottom drainage holes. Clay pots work well for lavender because their porosity provides better air circulation and drainage than plastic pots.

The term full sun refers to plant light requirements, but it has different meanings for different plants. For many plants, full sun means at least six hours of direct sunlight per day. For other plants, such as lavender, full sun means no shade.

A member of the mint family (Lamiaceae), lavender has square, grayish green stems and sparse leaves. The plant grows 1 to 3 feet tall with a wider spread, but its spikes of fragrant purple, blue, violet, pink or white flowers are the real attraction of this herb. Lavender grows as a perennial in U.S. Department of Agriculture plant hardiness zones 5 through 9, depending on its variety. Treat lavender as an annual in colder climates.

Although most lavender species -- English lavender (Lavandula angustifolia), which is perennial or hardy in USDA zones 5 through 8, French lavender (Lavandula dentata) and Spanish lavender (Lavandula stoechas), both hardy in USDA zones 8 through 9, and spike or French lace lavender (Lavandula multifida), hardy in USDA zones 6 through 8 -- may survive in partial shade, they grow with less vigor and produce fewer flowers with less fragrance than lavenders planted in sunny locations.

Lavender grows best in gravelly, sandy or sandy loam soil with a pH level of 6.4 to 8.2 and low fertility. Plant lavender in a raised bed or on an 18- to 24-inch mound within a perennial garden to ensure good drainage. Amend poorly draining soil with builder's sand to increase porosity. Change the structure of heavy clay soil by spreading 4 inches of sand or 1 inch of fine bark mulch on the planting bed and incorporating the material with the soil to a depth of 6 to 8 inches.

Get your lavender plant off to a good start by placing a double handful of 1-inch river rock and 1/2 cup of a mixture of equal parts of bone meal, composted manure and hydrated lime in the bottom of the planting hole, recommends Sunshine Lavender Farm on its website. With a hand trowel, mix the stone and amendments into the soil. Place 1/2 inch of non-amended soil over the mixture before placing the plant in the hole and firming the soil around it.

Root rot is the most common disease of lavender, and it can occur when the soil is not well-drained or when the plant is in a shady location. An affected plant wilts and declines. Its roots turn brown or black and die. Prevent the spread of root rot by removing the affected plant.

Nematodes, usually invisible to the naked eye, attack plant roots, causing galls that prevent water and nutrient absorption. A plant affected by nematodes loses vigor and may eventually die. The addition of organic matter such as composted manure and bark mulch to the soil can prevent nematode damage through the release of chemicals toxic to nematodes. Remove a nematode-affected plant, taking care to remove all of its roots from the soil.

The four-lined plant bug (Poecilocapsus lineatus) can damage lavender plants. This insect pest sucks sap from the leaves and stems of lavender, resulting in translucent or black spots and dying tissue. An adult four-lined plant bug is greenish yellow with four black lines down its back. Nymphs are crimson red and develop black wing pads as they grow. Organically control this pest by keeping all leaf litter removed from the growing site and clipping off egg masses during winter. The eggs can be found by examining plant stems, according to the University of Minnesota's VegEdge:

"During the fall, the banana shaped eggs are laid at right angles in vertical slits measuring 2 to 3 inches along the plant's stem. They are usually not laid individually but instead are laid in groups of six or more."

If the problem becomes serious, spray the lavender with a 1- to 2-percent insecticidal soap solution, prepared by mixing 2 1/2 to 5 tablespoons of insecticidal soap with 1 gallon of water. Apply the solution on a dry, calm day when the leaf temperature is below 85 degrees Fahrenheit. Wet all surfaces of the lavender with the solution for thorough coverage.

Wear skin and eye protection when using insecticidal soap: long pants, a long-sleeved shirt, goggles and chemical-resistant gloves. In the case of accidental exposure to eyes, flush them with water for 15 minutes. If skin is exposed, wash it with soap and water. Do not inhale insecticidal soap or a solution containing it. Seek medical attention if exposure occurs.